In cities, particularly large metropolitan areas, as more and more of the land surface becomes covered with buildings or paved with streets, parking lots, and the like, a significant problem exists with respect to the disposal of the water run-off which occurs during rain storms. Parking lots and streets typically are built with slopes toward storm drain outlets, which empty into underground storm sewers. In order to handle storm surges to inhibit overload of municipal systems, and to reduce pollutant entry into the drainage system, governments now typically require new construction sites to include a drainage management system.
Conventionally, storm drainage is often addressed using man-made ponds, large basins, or the like, designed from concrete and made to function as constructed wetlands. Because these basins are open to the atmosphere, they are subject to wide ranges of flooding and drying, with extensive evaporation frequently leading to desiccation and death of the wetland plants. An additional problem with these basins is that they form a pool, i.e., standing surface water. Unfortunately, standing water commonly result in a mosquito habitat, which can present both a nuisance and potentially a public health hazard. Furthermore, as pollutant concentrations can be expected to be high in this standing water, mosquitoes and other wildlife are subjected to elevated levels of bacteria, viruses, metals and hydrocarbons. This can result in both acute and chronic impacts to wildlife.
Alternatively, large beds of gravel surrounding a perforated pipe have been employed. In this embodiment, large pipes (diameters of 24 inches to 60 inches) are disposed horizontally in the desired drainage area at depths of up to about 4 feet. Stormwater from the surrounding area is diverted to and through the pipe when necessary.
What is needed in the art is a structurally sound, stormwater management system which does not consume development space, e.g. parking lot area, etc., and which handles the ebb and flow of the storm water.